PV
Section: User Manuals (1)
Updated: September 2021
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NAME
pv - monitor the progress of data through a pipe
SYNOPSIS
pv
[OPTION]
[FILE]...
pv
[-h|-V]
DESCRIPTION
pv
shows the progress of data through a pipeline by giving information such as
time elapsed, percentage completed (with progress bar), current throughput
rate, total data transferred, and ETA.
To use it, insert it in a pipeline between two processes, with the
appropriate options. Its standard input will be passed through to its
standard output and progress will be shown on standard error.
pv
will copy each supplied
FILE
in turn to standard output
(-
means standard input), or if no
FILEs
are specified just standard input is copied. This is the same behaviour
as
cat(1).
A simple example to watch how quickly a file is transferred using
nc(1):
-
pv file | nc -w 1 somewhere.com 3000
A similar example, transferring a file from another process and passing the
expected size to
pv:
-
cat file | pv -s 12345 | nc -w 1 somewhere.com 3000
A more complicated example using numeric output to feed into the
dialog(1)
program for a full-screen progress display:
-
(tar cf - . \
| pv -n -s $(du -sb . | awk '{print $1}') \
| gzip -9 > out.tgz) 2>&1 \
| dialog --gauge 'Progress' 7 70
Taking an image of a disk, skipping errors:
-
pv -EE /dev/your/disk/device > disk-image.img
Writing an image back to a disk:
-
pv disk-image.img > /dev/your/disk/device
Zeroing a disk:
-
pv < /dev/zero > /dev/your/disk/device
Note that if the input size cannot be calculated, and the output is a block
device, then the size of the block device will be used and
pv
will automatically stop at that size as if
-S
had been given.
(Linux only): Watching file descriptor 3 opened by another process 1234:
-
pv -d 1234:3
(Linux only): Watching all file descriptors used by process 1234:
-
pv -d 1234
OPTIONS
pv
takes many options, which are divided into display switches, output
modifiers, and general options.
DISPLAY SWITCHES
If no display switches are specified,
pv
behaves as if
-p, -t, -e, -r, and -b
had been given (i.e. everything except average rate is switched on).
Otherwise, only those display types that are explicitly switched on will be
shown.
- -p, --progress
-
Turn the progress bar on. If standard input is not a file and no
size was given (with the
-s
modifier), the progress bar cannot indicate how close to completion the
transfer is, so it will just move left and right to indicate that data is
moving.
- -t, --timer
-
Turn the timer on. This will display the total elapsed time that
pv
has been running for.
- -e, --eta
-
Turn the ETA timer on. This will attempt to guess, based on previous
transfer rates and the total data size, how long it will be before
completion. This option will have no effect if the total data size cannot
be determined.
- -I, --fineta
-
Turn the ETA timer on, but display the estimated local time of arrival
instead of time left. When the estimated time is more than 6 hours in the
future, the date is shown as well.
- -r, --rate
-
Turn the rate counter on. This will display the current rate of data
transfer.
- -a, --average-rate
-
Turn the average rate counter on. This will display the average rate of
data transfer so far.
- -b, --bytes
-
Turn the total byte counter on. This will display the total amount of
data transferred so far.
- -T, --buffer-percent
-
Turn on the transfer buffer percentage display. This will show the
percentage of the transfer buffer in use - but see the caveat under
%T
in the
FORMATTING
section below. Implies
-C.
- -A, --last-written NUM
-
Show the last
NUM
bytes written - but see the caveat under
%nA
in the
FORMATTING
section below. Implies
-C.
- -F, --format FORMAT
-
Ignore the options
-p,
-t,
-e,
-r,
-a,
-b,
-T,
and
-A,
and instead use the format string
FORMAT
to determine the output format. See the
FORMATTING
section below.
- -n, --numeric
-
Numeric output. Instead of giving a visual indication of progress,
pv
will give an integer percentage, one per line, on standard error, suitable
for piping (via convoluted redirection) into
dialog(1).
Note that
-f
is not required if
-n
is being used.
-
-
Note that if
--numeric
is in use, then adding
--bytes
will cause the number of bytes processed so far to be output instead of a
percentage; if
--line-mode
is also in use, then instead of bytes or a percentage, the number of lines
so far is output. And finally, if
--timer
is also in use, then each output line is prefixed with the elapsed time
so far, as a decimal number of seconds.
- -q, --quiet
-
No output. Useful if the
-L
option is being used on its own to just limit the transfer rate of a pipe.
OUTPUT MODIFIERS
- -W, --wait
-
Wait until the first byte has been transferred before showing any progress
information or calculating any ETAs. Useful if the program you are piping to
or from requires extra information before it starts, eg piping data into
gpg(1)
or
mcrypt(1)
which require a passphrase before data can be processed.
- -D, --delay-start SEC
-
Wait until
SEC
seconds have passed before showing any progress information, for example in
a script where you only want to show a progress bar if it starts taking a
long time. Note that this can be a decimal such as 0.5.
- -s SIZE, --size SIZE
-
Assume the total amount of data to be transferred is
SIZE
bytes when calculating percentages and ETAs. The same suffixes of "k", "m"
etc can be used as with
-L.
-
-
Has no effect if used with
-d PID
to watch all file descriptors of a process, but will work with
-d PID:FD.
- -l, --line-mode
-
Instead of counting bytes, count lines (newline characters). The progress
bar will only move when a new line is found, and the value passed to the
-s
option will be interpreted as a line count. Note that file sizes are not
automatically calculated when this option is used, to avoid having to read
all files twice.
- -0, --null
-
Count lines as null terminated. This option implies --line-mode.
- -i SEC, --interval SEC
-
Wait
SEC
seconds between updates. The default is to update every second.
Note that this can be a decimal such as 0.1.
- -w WIDTH, --width WIDTH
-
Assume the terminal is
WIDTH
characters wide, instead of trying to work it out (or assuming 80 if it
cannot be guessed).
- -H HEIGHT, --height HEIGHT
-
Assume the terminal is
HEIGHT
rows high, instead of trying to work it out (or assuming 25 if it
cannot be guessed).
- -N NAME, --name NAME
-
Prefix the output information with
NAME.
Useful in conjunction with
-c
if you have a complicated pipeline and you want to be able to tell different
parts of it apart.
- -f, --force
-
Force output. Normally,
pv
will not output any visual display if standard error is not a terminal.
This option forces it to do so.
- -c, --cursor
-
Use cursor positioning escape sequences instead of just using carriage
returns. This is useful in conjunction with
-N
(name) if you are using multiple
pv
invocations in a single, long, pipeline.
DATA TRANSFER MODIFIERS
- -L RATE, --rate-limit RATE
-
Limit the transfer to a maximum of
RATE
bytes per second. A suffix of "K", "M", "G", or "T" can be added to denote
kibibytes (*1024), mebibytes, and so on.
- -B BYTES, --buffer-size BYTES
-
Use a transfer buffer size of
BYTES
bytes. A suffix of "K", "M", "G", or "T" can be added to denote
kibibytes (*1024), mebibytes, and so on. The default buffer size is the
block size of the input file's filesystem multiplied by 32 (512KiB max), or
400KiB if the block size cannot be determined. This can be useful on
platforms like MacOS which perform better in pipelines with specific buffer
sizes such as 1024. Implies
-C.
- -C, --no-splice
-
Never use
splice(2),
even if it would normally be possible. The
splice(2)
system call is a more efficient way of transferring data from or to a pipe
than regular
read(2)
and
write(2),
but means that the transfer buffer may not be used. This prevents
-A
and
-T
from working, and makes
-B
redundant, so using
-A,
-T,
or
-B
automatically switches on
-C.
Switching on
-C
results in a small loss of transfer efficiency.
(This option has no effect on systems where
splice(2)
is unavailable).
- -E, --skip-errors
-
Ignore read errors by attempting to skip past the offending sections. The
corresponding parts of the output will be null bytes. At first only a few
bytes will be skipped, but if there are many errors in a row then the skips
will move up to chunks of 512. This is intended to be similar to
dd conv=sync,noerror
but has not been as thoroughly tested.
-
-
Specify
-E
twice to only report a read error once per file, instead of reporting each
byte range skipped.
- -S, --stop-at-size
-
If a size was specified with
-s,
stop transferring data once that many bytes have been written, instead of
continuing to the end of input.
- -d PID[:FD], --watchfd PID[:FD]
-
Instead of transferring data, watch file descriptor
FD
of process
PID,
and show its progress. The
pv
process will exit when
FD
either changes to a different file, changes read/write mode, or is closed;
other data transfer modifiers - and remote control - may not be used with
this option.
-
-
If only a
PID
is specified, then that process will be watched, and all regular files and
block devices it opens will be shown with a progress bar. The
pv
process will exit when process
PID
exits.
- -R PID, --remote PID
-
If
PID
is an instance of
pv
that is already running,
-R PID
will cause that instance to act as though it had been given
this instance's command line instead. For example, if
pv -L 123K
is running with process ID 9876, then running
pv -R 9876 -L 321K
will cause it to start using a rate limit of 321KiB instead of 123KiB.
Note that some options cannot be changed while running, such as
-c,
-l,
-f,
-D,
-E,
and
-S.
GENERAL OPTIONS
- -P FILE, --pidfile FILE
-
Save the process ID of
pv
in
FILE.
The file will be truncated if it already exists, and will be removed when
pv
exits. While
pv
is running, it will contain a single number - the process ID of
pv
- followed by a newline.
- -h, --help
-
Print a usage message on standard output and exit successfully.
- -V, --version
-
Print version information on standard output and exit successfully.
FORMATTING
If the
-F
option is given, then the output format is determined by the given format
string. Within that string, the following sequences can be used:
- %p
-
Progress bar.
Expands to fill the remaining space. Should only be specified once.
Equivalent to
-p.
- %t
-
Elapsed time. Equivalent to
-t.
- %e
-
ETA as time remaining. Equivalent to
-e.
- %I
-
ETA as local time of completion. Equivalent to
-I.
- %r
-
Current data transfer rate. Equivalent to
-r.
- %a
-
Average data transfer rate. Equivalent to
-a.
- %b
-
Bytes transferred so far (or lines if
-l
was specified). Equivalent to
-b.
- %T
-
Percentage of the transfer buffer in use. Equivalent to
-T.
Shows "{----}" if the transfer is being done with
splice(2),
since splicing to or from pipes does not use the buffer.
- %nA
-
Show the last
n
bytes written (e.g.
%16A
for the last 16 bytes).
Shows only dots if the transfer is being done with
splice(2),
since splicing to or from pipes does not use the buffer.
- %N
-
Name prefix given by
-N.
Padded to 9 characters with spaces, and suffixed with :.
- %%
-
A single %.
The format string equivalent of turning on all display switches is
`%N %b %T %t %r %a %p %e'.
COMMON SWITCHES
Some suggested common switch combinations:
- pv -ptebar
-
Show a progress bar, elapsed time, estimated completion time, byte counter,
average rate, and current rate.
- pv -betlap
-
Show a progress bar, elapsed time, estimated completion time, line counter,
and average rate, counting lines instead of bytes.
- pv -t
-
Show only the elapsed time - useful as a simple timer, e.g.
sleep 10m | pv -t.
- pv -pterb
-
The default behaviour: progress bar, elapsed time, estimated completion
time, current rate, and byte counter.
On MacOS, it may be useful to specify
-B 1024
in a pipeline, as this may improve performance.
EXIT STATUS
An exit status of 1 indicates a problem with the
-R
or
-P
options.
Any other exit status is a bitmask of the following:
- 2
-
One or more files could not be accessed,
stat(2)ed,
or opened.
- 4
-
An input file was the same as the output file.
- 8
-
Internal error with closing a file or moving to the next file.
- 16
-
There was an error while transferring data from one or more input files.
- 32
-
A signal was caught that caused an early exit.
- 64
-
Memory allocation failed.
A zero exit status indicates no problems.
AUTHOR
Written by Andrew Wood, with patches submitted by various other people.
Please see the package README for a complete list of contributors.
KNOWN PROBLEMS
The following problems are known to exist in
pv:
- *
-
The
-c
option does not work properly on Cygwin without
cygserver
running, if started near the bottom of the screen (IPC is needed to handle
the terminal scrolling). To fix this, start
cygserver
before using
pv -c.
- *
-
The
-R
option is not available on Cygwin without
cygserver
running (SYSV IPC is needed). To fix this, start
cygserver
before running the instance of
pv
you want, at runtime, to change the parameters of.
If you find any other problems, please report them.
REPORTING BUGS
Report bugs in
pv
to pv@ivarch.com or use the contact form linked from the
pv
home page: <http://www.ivarch.com/programs/pv.shtml>
SEE ALSO
cat(1),
dialog(1),
splice(2)
LICENSE
This is free software, distributed under the ARTISTIC 2.0 license.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- DISPLAY SWITCHES
-
- OUTPUT MODIFIERS
-
- DATA TRANSFER MODIFIERS
-
- GENERAL OPTIONS
-
- FORMATTING
-
- COMMON SWITCHES
-
- EXIT STATUS
-
- AUTHOR
-
- KNOWN PROBLEMS
-
- REPORTING BUGS
-
- SEE ALSO
-
- LICENSE
-
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Time: 15:00:51 GMT, May 18, 2024